Electronic switching circuit for electrically driven timepieces

ABSTRACT

An electronic switching circuit to operate mechanical vibrators for timepieces whose electric driving member consists of a coil and a permanent magnet. Said switching circuit allows an intensive amplitude control of the aforementioned mechanical vibrators.

United States Patent [191 [111 3,807,163 Meitinger Apr. 30, 1974 ELECTRONIC SWITCHING CIRCUIT FOR 1 10, 1 l3 ELECTRICALLY DRIVEN TIMEPIECES [76] Inventor: Heinz Meitinger, [56] Referenm Cited Theodor-Huess-Str. 16, Mutlangen, I UNITED STATES PATENTS Germany 3,046,460 7/1962 Zemla 58/23 A X [22] Filed Apr 17 1972 3,530,662 9/1970 Sch'dninger 58/23 R [21] Appl. No.: 244,457 Primary Examiner-Richard B. Wilkinson Assistant ExaminerEdith Simmons Jackmon [30] Foreigr; Application Pnorltv Data ABSTRACT I July 21, 19 1 Germany 2136329 An electronic Switching circuit to operate mechanical [52] U S Cl 58/23 58/23 TF 58/28 A vibrators for timepieces whose electric driving mem- T eds/132 ber consists of a coil and a permanent magnet. Said [51] Int. Cl l l G04c 3/00 switching circuit allows an intensive amplitude control [58] Field 'g' R 28 A of the aforementioned mechanical vibrators.

6 Claims, 2 Drawing Figures AAAAAA PATENTEDAPR so 1974 3.807 163 SHEET 1 or 2 FIG.1

ELECTRONIC SWITCHING CIRCUIT FOR ELECTRICALLY DRIVEN TIMEPIECES BACKGROUND OF THE INVENTION The conventional electronic drive circuits for the aforementioned object possess the disadvantage of having only a slight'stabilizing effect on the mechanical amplitude of vibration of the vibrator. This results in the mechanical amplitude'of vibration, after external disturbances and particularly after influences of acceleration, returning to the nominal value very slowly only. As mechanical vibrators possess the disadvantage, in practice, that they show different frequencies at various amplitudes, a deterioration of the rate accuracy results.

. SUMMARY OF THE INVENTION My invention aims at presenting a switching circuit with very strong stabilization of the amplitude of the mechanical vibrator at lowest possible costs. Thereby the mechanical vibrator is'to be primarily stabilized against amplitude disturbances of the mechanical type, i.e. friction changes and accelerations. In addition, the

amplitude must remain unchanged as far as possible in the case of changes of the electric driving voltage.

When employing semiconductor integrated circuits,

additional transistors cause only low excess costs, while coils always represent a high expense factor due to their sensitivity and the relatively expensive connection of the coil terminals. Thus, it is recommended, for reasons of economy, to strive for an approach with only one coil. Furthermore, this invention striving to realize an amplitude control by controlling the pulse width, enables the drive pulse to be put so favourablyin the range of the greatest electromotive force and therefore into that of the greatest efficiency, resulting even in a reduction in current consumption.

BRIEF DESCRIPTION OF THE DRAWINGS The special features as well as the functioning of the invention are described in conjunction with the accompanying drawings, in which:

FIG. 1 shows the circuit diagram of an embodiment of the electronic switching circuit.

- FIG. 2 shows'another embodiment.

DETAILED DESCRIPTION OF THE INVENTION The drive circuit corresponding to US. Pat. No. 3,046,460 by Zemla and being shown in all figures, is formed by a so-called complementary circuit comprising of working transistor A and complementary switching transistor S. As soon as complementary switching transistor S is turned on by a corresponding voltage in driving coil 20 or at condenser '2l, working transistor A islikewise turned on whereby driving coil 20 is connected to battery E, in a conducting switching circuit. Resistors 5 and 7 only serve as temperature stabilization or current restriction. Resistor 1 allows the drive circuit to be controlled as a function of the electromotive force induced in driving coil 20 by permanent magnet 22 which is moved relative to said driving coil 20. Permanent magnet 22 belonging to the mechanical structure of the timepiecewhich' does not form part of the instant invention is therefore not shown in detail. Said permanent magnet 22 is arranged in the conventional way and induces an electromotive force in driving coil 20 approximately during the greatest speed of the vibrator on which permanent magnet 22 is positioned. Condenser 21 forms along with resistor 6 a resistance-capacitor combination which causes the drive circuit to turn on impulsively in case signals of the electromotive force are missing.

Referring to FIG. 1, the mechanical amplitude of the vibrator must be represented by an electric signal in order to make amplitude control possible. As the electromotive force induced in driving coil 20 by permanent magnet 22 changes in the same proportion as the mechanical amplitude of driving coil 20, this electrical quantity is measured and used for influencing the pulse width of the driving current. The electromotive force cannot directly be tapped off in the case of the singlecoil systems as here the ohmic drop of voltage indriving coil 20 is always superimposed. In order'to still receive a voltage that varies in the same proportion as the electromotive forceof driving coil 20, a so-called bridge circuit is used consisting of resistors I, 2 and 3 as well'as of driving coil 20 anddiode D. Control tran-.

sistor R is operated by the control voltage generated in -'the diagonal arm of said bridge circuit, whereby the base of control transistor R- is connected to the bridge circuit between resistors 3 and 2, whereby the emitter of control transistor R is connected to the circuit between coil 20 and resistor 1. This special type of ci'rcuitry allows to turn on control transistor R in close dependence on the electromotive force of driving coil 20. Additional control transistor V which is complementarily switched with control transistor R then connects the base of complementary switching transistor S to the plus pole of battery E Thus, the voltage of condenser 21 is changed in such a manner that the voltage of coil 20 necessary to turn on the drive circuit is increased. This results in that, firstly, the driving pulse is shortened and furthermore the succeeding driving pulse is delayed as a greater electromotive force and longer charging-time are required for newly igniting the driving pulse. Excessive changes in the charging of condenser 21 and related control vibrations thereof can be suppressed by resistor 9. Diode D in the bridge circuit represents an equivalent of the threshold'volt'a'ge of control transistor R and serves as temperature stabilization. Resistors 3' to 6 are preferably designed as thickfilm resistors in view of'their size. Condenser 21 as well as driving coil 20 are also connected externally. The remaining switch circuit can be integrated. It is possible to adapt the integrated circuit to different types of timepieces because of the resistors and condensers, particularly resistor 3, being connected externally. In this respect, the large number of integrated circuits that is compulsory for the economy in integrated circuits can be achieved. The mechanical amplitude of the vibrator can be set to any valueb'y means of the adjustable resistor 3 Tests have shown that, in the case of the circuit shown in FIG. 1, the energy supplied to the vibrator changes 10 to 20 times more in the amount than the mechanical amplitude of the vibrator. When employing this'circuit the amplitudes of such vibrators whose electromotive force is much smaller than the threshold voltage of the usualtransistors can be stabilized. It goes without saying thatthe possible supply of energy, being determined by the geometric proportions of the motor and the electrical resistors in the coil circuit as well as by the electric voltage of power source.

E must be great enough to also allow the circuit to widen the pulse width and to increase the power supply therewith, in case'the mechanical amplitude is decreased by external influences.

The Equations 1 to 3, shown on page 6, allow the various components taking effect in the bridge circuit to be determined. The equation 3 shows that the compensation by diode D of the threshold voltage change of control transistor R that is subject to temperature takes place only imperfectly. The result could mean a reduction in amplitude of the mechanical vibrator at rising temperature. However, considering the fact that the magnet materials, particularly strontium/ferrite, that are generally used in timepieces have a negative temperature characteristic, the electromotive force induced in coil 20 decreases simultaneously with the threshold voltage at rising temperature, whereby the compensation error demonstrated in equation 3 is largely made up for. The compensation error according to equation 3 is due to the fact that E i.e., the threshold voltage of diode D, is not multiplied by the factor 1 but by the factor When the circuit is dimensioned according to equation 1, full compensation for the battery voltage change is achieved. If this is not required, the electromotive force at which the control is to start can be set to any value by tuning resistor 3 so that a wider range of applications for this switching circuit is given.

FIG. 2 represents a simplified form of construction of FIG. 1, whereby control transistor R is designed as PNP transistor whose collector is connected to the base of complementary switching transistor S.

In spite of the automatic control system being switched in parallel with the coil, a higher current consumption than without special amplitude control does not result due to the more favourable position of the driving pulse.

Equations 1 to 3 to determine the components according to FIG. 1:

Equation 1 is for full compensation for the battery voltage changes:

R resistance of coil U, voltage from base to emitter of control transistor R a The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims.

I claim:

1. Electronic switching circuit for driving an electric timepiece which contains a bridge circuit consisting of a transistorized circuit generating a control voltage by a combination of resistors which are connected together to form a bridge circuit, whereby the driving coil is one of the components of said bridge circuit, the voltage generated in the diagonal arm of said bridge circuit being used to change the pulse width in the sense contrary to the electromotive force induced in said driving coil by a permanent magnet which is moved relative to said driving coil, the change of the pulse width being achieved by charging and discharging a condenser being connected between the input of the drive circuit and one terminal of said driving coil and herewith influencing the switching voltage of said drive circuit, said condenser being charged and discharged by a control transistor which is operated by the control voltage generated by said bridge circuit.

2. Electronic switching circuit in accordance with claim 1 wherein base and emitter of said control transistor are positioned in said diagonal arm of said bridge circuit and the collector of said control transistor is connected to one terminal of said condenser in order to allow the charging voltage of said condenser being changed.

3. Electronic switching circuit in accordance with claim 1 wherein said. control transistor is designed as a transistor whose base-emitter-path is positioned in said diagonal arm of'said bridge circuit and whose collector is connected to the base of anadditional control transistor which charges and discharges said condenser.

4. Electronic switching circuit in accordance with claim 1 wherein the charging and discharging of said condenser caused by said control transistor can only occur simultaneously with the driving pulse.

5. Electronic switching circuit in accordance with claim 1 wherein charging or discharging of said condenser by said control transistor can only arise by an electromotive force being poled in such a manner that it could likewise fire said drive circuit. 1

-6. Electronic switching circuit in accordance with claim 1 wherein a diode is placed in one arm of said bridge circuit in such a manner that the voltage change of said diode caused by a temperature change changes the control voltage of said bridge circuit fora similar amount as the base-emitter voltage of said control transistor changes under the influence of said temperature change. 7

l #IK 

1. Electronic switching circuit for driving an electric timepiece which contains a bridge circuit consisting of a transistorized circuit generating a control voltage by a combination of resistors which are connected together to form a bridge circuit, whereby the driving coil is one of the components of said bridge circuit, the voltage generated in the diagonal arm of said bridge circuit being used to change the pulse width in the sense contrary to the electromotive force induced in said driving coil by a permanent magnet which is moved relative to said driving coil, the change of the pulse width being achieved by charging and discharging a condenser being connected between the input of the drive circuit and one terminal of said driving coil and herewith influencing the switching voltage of said drive circuit, said condenser being charged and discharged by a control transistor which is operated by the control voltage generated by said bridge circuit.
 2. Electronic switching circuit in accordance with claim 1 wherein base and emitter of said control transistor are positioned in said diaGonal arm of said bridge circuit and the collector of said control transistor is connected to one terminal of said condenser in order to allow the charging voltage of said condenser being changed.
 3. Electronic switching circuit in accordance with claim 1 wherein said control transistor is designed as a transistor whose base-emitter-path is positioned in said diagonal arm of said bridge circuit and whose collector is connected to the base of an additional control transistor which charges and discharges said condenser.
 4. Electronic switching circuit in accordance with claim 1 wherein the charging and discharging of said condenser caused by said control transistor can only occur simultaneously with the driving pulse.
 5. Electronic switching circuit in accordance with claim 1 wherein charging or discharging of said condenser by said control transistor can only arise by an electromotive force being poled in such a manner that it could likewise fire said drive circuit.
 6. Electronic switching circuit in accordance with claim 1 wherein a diode is placed in one arm of said bridge circuit in such a manner that the voltage change of said diode caused by a temperature change changes the control voltage of said bridge circuit for a similar amount as the base-emitter voltage of said control transistor changes under the influence of said temperature change. 